In the gas phase process for the production of polyolefin polymers such as polyethylene polymers, one or more gaseous alkenes (e.g., ethylene, butene, propene, etc.), hydrogen, co-monomer and other materials produce a solid polyolefin product. Generally, gas phase polymerization systems typically include a fluidized bed reactor, a compressor, and a cooler. The reaction is maintained in a two-phase fluidized bed of granular polyethylene polymers and gaseous reactants by the fluidizing gas which is passed through a distributor plate near the bottom of the reactor vessel. The reactor vessel is normally constructed of carbon steel and rated for operation at pressures, for example, up to about 50 bars (or about 3.1 MPa). Catalyst is injected into the fluidized bed. Heat of reaction is transferred to the circulating gas stream. This gas stream is compressed and cooled in the external cycle line and then is reintroduced into the bottom of the reactor where it passes through a distributor plate. Make-up feedstreams and optionally other materials are added to maintain the desired reactant concentrations.
While the reactor's internal disengagement section removes a substantial amount of particles, it is typical for small particulates of catalyst and polymer product to become entrained in the cycle gas stream. Commonly in processes in which a portion of the remaining entrained particulates are removed from the cycle gas stream, the particulates are removed after the outlet of the reactor and before the cycle gas reaches the compressor e.g., typically using one or more cyclones. See, for example, U.S. Pat. Nos. 5,922,818, and 6,911,504.